In recent years, polymers and plastics have become increasingly popular and important materials for making various types of articles. These articles, in turn, have been used in a limitless variety of applications. For instance, polymers and plastics are typically used as containers for various articles, such as food items. In some applications, an item contained in a polymeric or plastic article can be subject to attack and contamination by microorganisms. As such, a polymeric or plastic material capable of destroying or inhibiting foreign microorganisms would be highly desirable.
Bacterial contamination of food, especially meat products, has become the focus of growing concern among public health professionals. In 1993, over 500 individuals became ill, and five people died, after eating hamburgers purchased from fast food restaurants. The causative organism, E. Coli 0157:H7, is most often associated with ground beef.
Recently, the coccidian parasite Cyclorspora was implicated in an outbreak of gastrointestinal illness among school children, who had ingested contaminated strawberries served for school lunch. Such infection may result in a protracted illness, characterized by frequent, watery stools and other gastrointestinal symptoms; symptoms which may remit and relapse. Although antibiotic therapy is effective to shorten the clinical course associated with Cyclospora infection, no treatment regimen has been identified for patients who cannot tolerate sulfa drugs (MMWR, 46:451, May 23, 1997).
Contamination of foodstuffs by viruses and parasites has recently become of growing concern, because the resulting infections often are refractory to drug treatment. In the majority of persons, the body's immune system is able to limit the replication of such infectious agents, leading to the eventual control and resolution of clinical disease. However, in immunocompromised individuals, such as those suffering from cancer or AIDS, the immune system may not be able to control infection, resulting in a much more serious prognosis.
Although some of the problems associated with microbial contamination of food can be addressed by improved handling and preparation techniques, methods which would reduce contamination during packaging and storage would also significantly decrease the risks associated with food-borne contamination.
A number of methods have been proposed to reduce microbial contamination in foodstuffs prior to preparation. Improvements in poultry processing methods, for example, have reduced the risk of salmonella food poisoning. However, contamination still occurs and any microorganisms present will continue to replicate once the meat is packaged. Thus, special care is still required during storage and handling to prevent food poisoning caused by the ingestion of pathogenic microbes.
During packaging, the treatment of foodstuffs with agents capable of reducing or eliminating microorganisms would decrease the risks associated with food-borne illnesses. However, most of these agents are themselves associated with unacceptable safety risks.
For example, irradiating fruit and milk has been shown to reduce microbial contamination, but safety concerns have prevented the wide-spread acceptance of irradiated products.
The use of antimicrobials could also effectively reduce contamination associated with foodstuffs. However, because the use of such drugs has been associated with the development of resistant organisms, such an approach is currently impractical.
However, many naturally occurring plants and herbs have been shown to possess antimicrobial activity and their use has been shown to be safe for human and animal consumption. Extracts of such plants and herbs, known as phytochemicals or phytonutrients, may be useful to reduce microbial contamination during the processing and storage of foodstuffs, while providing the added advantage of being safe for contact with consumables.
The present invention is concerned with reducing microbial contamination of organic materials, including but not limited to the processing and storage of foodstuffs. Other uses include treating bio-fouling problems associated with the production of a biofilm on marine and industrial equipment. Currently the treatment of bio-fouling includes the use of toxic chemicals, thus creating waste problems with biohazerdous material. In general terms, the present invention relates to the incorporation of antimicrobial agents into polymeric materials, such that the activity of the agents will reduce the microbial contamination of the organic material with which it comes in contact. In a particular application for plastic food wrappers, antimicrobial agents are mixed with polymer compositions during formation of the plastic sheeting and molded containers and thereafter reduce or destroy the bacteria on that portion of the foodstuffs with which it comes into contact. Plastic sheeting for food wrappers and plastic containers are only two specific applications for the composition of the present invention.
The prior art discloses a number of examples of plastic materials containing antimicrobial agents, but none have the particular characteristics of the present invention.
For instance, U.S. Pat. No. 5,554,373 to Seabrook et al., which is incorporated herein by reference in its entirety, discloses compositions containing antimicrobial agents and a chemical controller, which functions to regulate the release rate of the antimicrobial agent. One of the biocidal agents disclosed is 10,10-oxybisphenoxarsine, which is an organically bound arsenic and will be referred to hereinafter as OBPA.
U.S. Pat. No. 4,888,175 to Burton, et al., discloses a plastic packaging material having a biocidal agent dissolved or dispersed therein. The biocidal agent disclosed is OBPA. The plastic material can be formed into a package for containing an organic material susceptible to bacterial or viral attack.
U.S. Pat. No. 4,666,956 to Spielau, et al. discloses a biocidal composition based on organic arsenic compounds. A tin compound is added to the composition to prevent elution of the arsenic compound. The compositions are used in the production of molded plastic articles, especially those vulnerable to biological attack.
U.S. Pat. Nos. 4,624,679 and 4,891,391, both to McEntee, disclose an antimicrobial and anti-oxidant composition preferably incorporated into a thermoplastic resin. The antimicrobial agents are incorporated into the thermoplastic materials during fabrication so that the resulting thermoplastic articles will resist microbial growth. The anti-oxidant is added so that the antimicrobial agent does not degrade during processing. OBPA is disclosed as one of the microbiocides.
An assortment of compositions containing microbiocides are disclosed in U.S. Pat. Nos. 4,686,239, 4,789,692, 4,086,297, and 4,663,077 in which Rei is listed as an inventor. In the '239 patent, the '692 patent, and the '297 patent, a composition is disclosed wherein a microbiocide in high concentrations is added to a thermoplastic resin. The resulting concentrate is then incorporated into a second thermoplastic resin to produce a resulting article having the appropriate level of microbiocide. The second thermoplastic resin is added in an attempt to control the mobility of the microbiocide. One of the microbiocides disclosed is OBPA.
The '077 patent discloses a microbiocidal solution comprising an aryl alkanol solvent and a microbiocide compound dissolved therein. A plasticizer suitable for use as a polymer processing aid is added to the composition.
Anti-bacterial materials and antimicrobial mixtures are disclosed in United Kingdom Patent No. 1,169,288 and European Patent Application No. 84113170.9. The United Kingdom patent is directed to a material having a base sheet of plastic coated on one surface with a polymeric liquid composition containing an anti-bacterial agent capable of migrating through the sheet. The European patent application, on the other hand, discloses a mixture of a phenoxyarsine as an antimicrobial agent and a solvent. A plasticizer can be added to the mixture for incorporation into plastics.
Other prior art compositions containing biocides include U.S. Pat. No. 4,747,902 to Saitoh, U.S. Pat. No. 3,864,468 to Hyman et a1., U.S. Pat. No. 4,666,706 to Farquharson et al., U.S. Pat. No. 5,063,706 to Aki et al., and U.S. Pat. No. 4,876,070 to Tsukahara et al.
Although the prior art shows a combination of biocidal compositions, the particular features of the present invention remain absent. Some of the prior art discloses materials containing small amounts of biocidal compositions for preventing bacterial attack on the material itself. However, most of the prior art does not show the use of biocidal materials in packaging films or sheets at a level such that the contents of the package, instead of the plastic itself, are inhibited against bacterial or viral growth. Further, the prior art is generally deficient in affording a composition that will not only control bacterial growth, but will also simultaneously control the growth of fungi, viruses, and parasites.
Although it is known in the prior art to incorporate antimicrobial agents into plastics, the plastic products generally cannot be used for food applications unless extremely small amounts of biocides are used because the biocides may be harmful to humans. However, small quantities of biocide will not protect the contents of the package adequately or protect the contents for an effective length of time from attack. Consequently, a need exists for a polymeric material containing antimicrobial agents which is safe for human and animal contact and which is safe for contact with human and animal consumables. Further still, although some of the prior art discloses the incorporation of antimicrobial agents with activity specifically against bacteria, a need exists for an antimicrobial composition that will simultaneously inhibit the growth of fungi, viruses, actinomycetes and parasites, as well as bacteria.